PSI - Issue 65

Maslov S.V. et al. / Procedia Structural Integrity 65 (2024) 139–146 Author name / Structural Integrity Procedia 00 (2024) 000–000

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where σ k are the required axial stresses; ε k are the measured values of deformations; K is the volumetric modulus of elasticity of the material; σ i and ε i are the intensities of stresses and deformations, respectively; ε 0 are the average stresses. 4. If the stress intensity becomes less than the yield strength, further calculation is done according to the formulas (5). The developed technique is used to process the findings of SSS field studies for an intermediate heat exchanger of the BN type reactor (Babushkin S.V. et al, 2020). The experimentally obtained and corrected stress change functions in the interface zone of the shell with the plate of the protection unit are shown in Fig. 4. In the interface zone of the shell with the massive plate of the protection unit where strain gauges 9/10 and 37/38 are installed, zones of local elastic-plastic deformations occur when emergency protection is activated. Therefore, the functions obtained using the classical formulas (4) are adjusted to take into account the inelastic behavior of the structural material. The extreme values of the corrected functions are indicated in Fig. 4 by an additional "asterisk".

Fig. 4. Stress in the heat exchanger top plate in emergency conditions.

6. Results and summary

The considered method for determining and accounting for the creep effect of strain gauges, which occurs under variable measured deformations and high temperatures, allows minimizing and taking into account the limits of possible error associated with this effect. The proposed technique based on the use of real deformation diagrams makes it possible to clarify the stress change functions determined by strain measurements during transitions between elastic and elastic-plastic behaviors of the material.

References

Makhutov N.A., Matvienko Yu.G., Romanov A.N., et al., 2018. Problems of strength, technogenic safety and structural materials science. Moscow, Lenand Publishing House, 2018, p.p. 720. (In Russian). EDN: YPBGTB Volkov I.A., Igumnov L.A., Shishulin D.N., Pichkov S.N., 2023. Assessment of service life characteristics of power equipment parts under thermal cyclic loading. Problems of Strength and Plasticity, 1, 96-119. DOI: 10.32326/1814-9146-2023-85-1-96-119. EDN: BUNSFA